That is what I observe also. So much for the "There are plenty of studies proving conclusively that almost no observers get any more detail with binoculars over about ~10x magnification. You need a tripod or at least a monopod to get any real benefit from magnfications above ~10x." theory. The graph makes me realize how much more efficient the Fujinon 12x28 and 16x28 Techno-Stabi stabilized binoculars are than a normal 12x or 16x binocular handheld. The efficiency goes up from 6 to 10 for handheld to supported. Almost doubles.Your link there (not just its text label) got truncated with "..." and is unusable; the correct link is here.
What's interesting about that graph is that it does not show a "decline in efficiency" with increasing magnification. To the contrary, it shows increasing efficiency, even handheld, up to around 15x where it starts to level off. Only the rate of increase is declining. That seems to agree well with my own experience.